U.S. Pat. No. 4,921,767, issued to Datta et al., on May 1, 1990, describes a method for electrophotographically manufacturing a luminescent screen assembly on an interior surface of a CRT faceplate using dry-powdered, triboelectrically charged, screen structure materials deposited on a suitably prepared, electrostatically chargeable surface.. The chargeable surface, or photoreceptor, comprises an organic photoconductive layer overlying a conductive layer, both of which are deposited, serially, as solutions on the interior surface of the CRT panel.
The photoconductive layer of the aforementioned patent comprises a volatilizable organic polymeric material such as polyvinyl carbazole (pvk), or an organic monomer such as n-ethyl carbazole, n-vinyl carbazole or tetraphyenylbutatriene (TPBT). Drawbacks of the preferred PVK photoconductive materials are that they tend to crack during filming, phosphor deposits do not adhere satisfactorily during fixing, and a long time is required to bake out the volatilizable constituents of the layer during screen bake. A drawback of TPBT is that it has poor solubility, tends to crystallize and has no appreciable sensitivity in the wavelength of current interest, i.e., 400-500 nm. The crystallization is objectionable because electrical breakdown occurs at the crystal sites and produces phosphor and/or matrix defects at these sites.
A need exists for suitable materials without the shortcomings of the known materials and which can be charged to about 400 to 600 volts, without dielectric breakdown. Additionally, the materials should have little or no dissipation of the electric charge in the dark, but discharge rapidly when illuminated with light. Additionally, it is desirable that the materials have no spectral sensitivity beyond 550 nm, so that the screening process can be done in yellow light, rather than in the dark, to provide a safe manufacturing environment.